Yeah, it could be the aggressive feed ramp in the new M4's that was part of the problem.
With that said, I never had one FTF or FTE or mashed in projectiles before that day, and I always used factory ammo and brand new P-mags.
Also, I never had a problem with Wild Turkey's loads before that day, either. I can't remember if I was using my P-mags or Wild Turkey's mags, though. I think some of both.
It was fun to have to be forced to work with a bunch of failures that day. Gave me a lot of good practice.